This invention relates generally to atomic particle detection apparatus and, more particularly, to methods and apparatus for detecting neutrons in a negative pressure environment.
Neutron bombardment and scattering experiments are performed in some facilities, including facilities that perform material detection research. Some known material detection experiments include positioning a material of interest into a chamber that typically includes a neutron source and at least one neutron detector array that is positioned at a pre-determined distance from the neutron source. The material is positioned between the neutron source and the neutron detector array. Some known neutron sources generate a pre-determined neutron flux that includes neutrons having energies less than 3.2×10−12 Joules (J) (20 mega-electron-volts (MeV)), that is, low energy neutrons. Such neutrons generally interact with the material of interest and interaction may scatter the neutrons from their original transport paths in a manner consistent with the properties of the material of interest. For example, the paths may be altered based on the densities and neutron cross-sections of the material's constituents. At least some of the scattered neutrons interact with the neutron detection array that facilitates a collection of data associated with at least some of the neutrons' properties, including, but not limited to, the number of neutrons interacting with the array. Some known arrays include position sensitive detectors (PSDs) that are configured to record where atomic particle interaction occurs within the detector. Such position data facilitates the study of atomic particle interactions.
Some known PSDs detect neutrons in an environment that includes air. The air facilitates undesirable scattering and attenuation of neutrons that may mitigate the effectiveness of the detection array, which may subsequently have a deleterious effect on the effectiveness of the experiments. Alternatively, some known PSDs operate in a negative pressure environment wherein a large number of PSDs in the array directly correlate to an equally large number of vacuum seals positioned between the negative pressure environment and adjacent positive pressure environments. Decreasing a diameter of the PSDs, while increasing the number of PSDs for a given volume, facilitates increasing an efficiency and effectiveness of particle detection by the array. However, increasing the number of PSDs also increases the number of vacuum seals required, and as such also increases the fabrication and installation costs associated with the array. In addition, the increased number of PSDs may also increase a potential for seal malfunction.